A conventional practice in this field is to attach a video camera to a microscope, in order to generate signals that are representative of an image in the field of view of the microscope. Such signals are fed to a computer having a capture card (frame grabber), and the resultant image is displayed on the monitor. The display on the monitor typically has a resolution in the order of 640 by 480 pixels, provided the resolution of the camera is equal to or greater than this value. When using modern laboratory microscope at a low power objective such as 1.times., 2.5.times., 4.times., the field of view, which is circular, ranges from about 20 mm to 5 mm, although certain more expensive research instruments can have a field of view in the order of 28 mm to 7 mm. When a video camera is attached to the microscope the field of view decreases to about 10 mm to 2.5 mm, since the camera will have a rectangular field of view with an aspect ratio of 4 to 3. Thus the largest rectangular field of view that a typical video camera can display when attached to a microscope is about 10mm.times.7.5 min. This severely limits the size of the largest tissue sample image that can be viewed on a monitor to such size, namely 10mm.times.7.5 mm.
Moreover, a typical laboratory microscope video camera and display system is very expensive, and can cost in the range of from $10,000-$15,000 or more, excluding the cost of the microscope. To obtain larger fields of view and higher capture and display resolutions, the above-mentioned research microscopes can be used with additional intermediate lenses and higher performance capture and display electronics. However such systems cost tens of thousands of dollars more than the typical systems.
Microscope specimen slides that are viewed through a microscope usually are made of glass and commonly are rectangular having side dimensions of 1 in..times.3 in. The thickness dimension is 1.1 mm. A sample of histological tissue is prepared and sliced to a very thin section (3 to 5 microns), which is mounted on the glass slide and protected by a rectangular coverslip that has dimensions of 40 mm long.times.20 mm wide.times.0.15 mm thick. The coverslip limits the size of the largest tissue sample that can be mounted. Such slides are viewed by pathologists, anatomists and biologists and the like on a daily, routine basis. Indeed literally millions of such slides are created and viewed by thousands of researchers and clinicians every day, so that improvements in accordance with this invention have wide application in the art.
As noted above, where the size of the tissue sample exceeds 10 mm.times.7.5 mm, the use of a microscope and video camera to capture and display an image thereof has an inherent, very serious problem. Even though the specimen slide and coverslip can accommodate a fairly large tissue sample section, for example up to 40 mm.times.24 mm, there is no way when using conventional technology to display the entire sample section for viewing by the clinician. Of course as a practical matter, the side dimensions of a slide do not exceed 36 mm.times.24 mm.
It is an object of the present invention to provide a new and improved imaging system that enables display of large tissue samples at high resolution.
Another object of the present invention is to provide a new and improved imaging system that employs a scanner and a unique slide holder that enables display of the entirety of a large tissue sample with high resolution.
Yet another object of the present invention is to provide a new and improved holder for a tissue sample slide, such holder including a glass filter having neutral density to reduce the amount of light transmitted through the slide by a predetermined amount without affecting the Kelvin temperature of such light.